Lots of good reads listed already, I'll throw in the following:
1. The Practice of Freedom by Wendy Palmer
2. Sword and Brush by Dave Lowery
3. Martial Meditations by Kim and Back

Favorites for motivation are Angry White Pajamas and In Search of the Warrior Spirit; Favorites for catalyst in connection and spiritual approach are Aikido and Harmony of Nature and Practice of Freedom; favorites for focus on Budo include Bushido (Nitobe) and Autumn Lightning.

There are a great number of wonderful books I have on my shelf I have not mentioned and have read multiple times, but these tend to stick out in my mind.